Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, SP, Brazil.
Departamento de Patologia, Programa de Pós Graduação em Biotecnologia do Renorbio, Ponto Focal Maranhão, Universidade Federal do Maranhão, São Luís, MA, Brazil.
PLoS Negl Trop Dis. 2019 Sep 6;13(9):e0007734. doi: 10.1371/journal.pntd.0007734. eCollection 2019 Sep.
Brazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, has been associated with the transmission by the tick Amblyomma sculptum, and one of its main hosts, the capybara (Hydrochoerus hydrochaeris).
During 2015-2019, we captured capybaras and ticks in seven highly anthropic areas of São Paulo state (three endemic and four nonendemic for BSF) and in two natural areas of the Pantanal biome, all with established populations of capybaras.
The BSF-endemic areas were characterized by much higher tick burdens on both capybaras and in the environment, when compared to the BSF-nonendemic areas. Only two tick species (A. sculptum and Amblyomma dubitatum) were found in the anthropic areas; however, with a great predominance of A. sculptum (≈90% of all ticks) in the endemic areas, in contrast to a slight predominance of A. dubitatum (≈60%) in the nonendemic areas. Tick species richness was higher in the natural areas, where six species were found, albeit with a predominance of A. sculptum (≈95% of all ticks) and environmental tick burdens much lower than in the anthropic areas. The BSF-endemic areas were characterized by overgrowth populations of A. sculptum that were sustained chiefly by capybaras, and decreased populations of A. dubitatum. In contrast, the BSF-nonendemic areas with landscape similar to the endemic areas differed by having lower tick burdens and a slight predominance of A. dubitatum over A.sculptum, both sustained chiefly by capybaras. While multiple medium- to large-sized mammals have been incriminated as important hosts for A. sculptum in the natural areas, the capybara was the only important host for this tick in the anthropic areas.
The uneven distribution of R. rickettsii infection among A. sculptum populations in highly anthropic areas of São Paulo state could be related to the tick population size and its proportion to sympatric A. dubitatum populations.
巴西斑疹热（BSF）由立克次体细菌立氏立克次体引起，与通过硬蜱 Amblyomma sculptum 的传播有关，而该蜱虫的主要宿主之一是水豚（Hydrochoerus hydrochaeris）。
在 2015 年至 2019 年期间，我们在圣保罗州的七个高度人为化地区（三个 BSF 流行地区和四个非 BSF 流行地区）以及潘塔纳尔生物群落的两个自然地区捕获了水豚和蜱虫，这些地区都有稳定的水豚种群。
与 BSF 非流行地区相比，BSF 流行地区的水豚和环境中的蜱虫负担要高得多。在人为地区仅发现了两种蜱虫（A. sculptum 和 Amblyomma dubitatum）；然而，在流行地区，A. sculptum 占主导地位（≈90%的所有蜱虫），而在非流行地区，A. dubitatum 占主导地位（≈60%）。在自然地区，发现了六种蜱虫，物种丰富度更高，尽管 A. sculptum 占主导地位（≈95%的所有蜱虫），但环境中的蜱虫负担要比人为地区低得多。BSF 流行地区的 A. sculptum 过度生长，主要由水豚维持，而 A. dubitatum 种群减少。相比之下，景观与流行地区相似的 BSF 非流行地区，蜱虫负担较低，A. dubitatum 对 A. sculptum 略占优势，两者均主要由水豚维持。虽然在自然地区，多种中大型哺乳动物被认为是 A. sculptum 的重要宿主，但水豚是该蜱虫在人为地区的唯一重要宿主。
在圣保罗州高度人为化地区的 A. sculptum 种群中，立氏立克次体感染的分布不均，可能与蜱虫种群规模及其与共生的 A. dubitatum 种群的比例有关。
